Alteration Mineralogy and Geochemistry of the...

Alteration Mineralogy and Geochemistry of theHydrothermally Altered Rocks of the Kutlular (Sürmene)

Massive Sulfide Deposit, NE Turkey

EMEL ABDİOĞLU & MEHMET ARSLAN

Department of Geological Engineering, Karadeniz Technical University,TR–61080 Trabzon, Turkey

(E–mail: [email protected])

Received 01 April 2007; revised typescript received 06 December 2007; accepted 13 February 2008

Abstract: Volcanogenic massive sulfide deposits accompanying the Upper Cretaceous felsic rocks in the intra-arc rift zone of thePontide palaeo-arc are common in the NE Turkey. One of them, the Kutlular (Sürmene, Trabzon) deposit, is an abandoned minewithin the Upper Cretaceous mafic, felsic volcanics and subvolcanic rocks.

Detailed mineralogical and geochemical studies indicate the presence of hydrothermal alteration zones around the Kutlulardeposit; these alteration zones are represented by silicification-pyrite-illite zone, illite-silicification zone, illite/smectite-silicificationzone, smectite zone accompanying kaolinite and halloysite in the dacitic pyroclastics, and additionally chlorite zone in the maficvolcanics. Lithogeochemical data indicate that the footwall dacitic rocks (Zr/Y= 1.39–16.39, La/Yb= 0.14–9.57) and hanging-wallbasalts-basaltic andesites (Zr/Y= 2.13–5.65, La/Yb= 1.16–5.00) are transitional between tholeiitic and calc-alkaline in character. Thetrace element patterns of the rocks show considerable LILE enrichment (K, Rb and Ba) and depletion in Sr and Ti relative to N-typeMORB. Chondrite-normalized REE patterns of the footwall show pronounced HREE enrichment. The Kutlular footwall and hangingwall alteration zones have several geochemical characteristics that show systematic changes with increasing proximity to ore bodysuch as Na depletion as well as elevated alteration index (AI) and chlorite-carbonate-pyrite index (CCPI). Generally, hanging-wall maficvolcanics and footwall rocks have high CCPI (chlorite-carbonate-pyrite index) values, indicating the importance of chlorite and pyriteformation in these rocks. Calculated mass changes in the footwall dacites commonly are large, and result from major silica masstransfer (–9.11 to 99.68 g/100 g rock). Mass-change calculations indicate that CaO + Na2O + MgO were leached from the rocks byhydrothermal solutions, whereas large amounts of hydrothermal iron were added. Hanging wall basalt and basaltic andesite showsmass changes that are generally much smaller than in the footwall.

Key Words: hydrothermal alteration, clay minerals, massive sulfide deposit, eastern Pontides, Turkey

Kutlular (Sürmene, Trabzon) Masif Sülfit Yatağı Çevresindeki Hidrotermal Altere KayaçlarınAlterasyon Mineralojisi ve Jeokimyaları, KD Türkiye

Özet: Eski bir adayayı kalıntısı olan Pontidler’de yay içi rift zonunda oluşan Geç Kretase yaşlı felsik kayaçlar volkanojenik masif sülfityataklarına ev sahipliği yaparlar. Bunların arasında, terkedilmiş bir maden olan Kutlular masif sülfit yatağı (Sürmene, Trabzon) GeçKretase yaşlı mafik, felsik ve subvolkanik kayaçları içerir.

Ayrıntılı mineralojik ve jeokimyasal çalışmalar Kutlular yatağı çevresinde hidrotermal alterasyon zonlarının varlığını göstermiştir.Bu zonlar; dasitik piroklastitlerde silisleşme-pirit-illit zonu, illit-silisleşme zonu, illit/simektit-silisleşme zonu, simektit zonu ve bunaeşlik eden kaolenit ve halloysit ile temsil edilirken, mafik volkanitlerde klorit zonu iyi gelişmiştir. Litokimyasal veriler ışığında cevherlidasitik kayaçlar (Zr/Y= 1.39–16.39, La/Yb= 0.14–9.57) ve örtü kayaçları olan bazaltik-andezitik kayaçlar (Zr/Y= 2.13–5.65, La/Yb=1.16–5.00) toleyitik-kalkalkalen karakterlidir. Tüketilmiş okyanus ortası sırtı bazaltına (N-MORB) normalize iz element değişimlerinegöre örnekler büyük iyon yarıçaplı litofil elementler (LILE; K, Rb ve Ba) bakımından zenginleşmiş, Sr ve Ti bakımından isetüketilmişlerdir. Cevherin içerisinde bulunduğu dasitik kayaçların kondrite normalize nadir toprak element (REE) değişimleri ağırnadir toprak elementler (HREE) bakımından zenginleşme göstermektedir. Kutlular madeni taban ve örtü kayaçları alterasyon zonlarıcevhere yaklaştıkça sistematik olarak Na’ca tüketilme, alterasyon indeksi (AI) ve klorit-karbonat-pirit indeksinde (CCPI) artışlarla ifadeedilebilecek jeokimyasal karakteristikler sergilerler. CCPI değeri örtü kayaçları konumundaki mafik volkanitler ve cevherin içerisindebulunduğu felsik kayaçlarda kloritleşme ve pirit oluşumunun önemini ifade eder şekilde yüksektir. Cevherli dasitlerde hesaplanan kütledeğişimi oldukça büyüktür ve genelde SiO2’deki değişimlerden kaynaklanır (–9.11 to 99.68 gr/100 gr kayaç). Kütle değişimhesaplarına göre CaO + Na2O + MgO hidrotermal akışkanlarca kayaçlardan yıkanmış; buna karşın büyük miktarda demir eklenmiştir.Örtü kayaçları bazalt ve bazaltik andezitler kütle değişiminden daha az oranda etkilenmişlerdir.

Anahtar Sözcükler: hidrotermal alterasyon, kil mineralleri, masif sülfit yatağı, Doğu Pontidler, Türkiye

Introduction

Volcanogenic massive Cu-Zn-(Pb) sulfide (VMS) depositsdevelop primarily in subaqueous rift-related environments(e.g., oceanic, fore-arc, arc, back-arc, continental margin,

or continental), and are hosted primarily by bimodal,mafic-felsic volcanic successions, with specific geochemicalcharacteristics (e.g., Hart et al. 2004). The easternPontide volcanic province is part of the Tethyan-Eurasia

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Turkish Journal of Earth Sciences (Turkish J. Earth Sci.), Vol. 18, 2009, pp. 139–162. Copyright ©TÜBİTAKdoi:10.3906/yer-0806-7 First published online 07 July 2008

metallogenic belt, which extends from east Europe tomiddle Asia-Pacific and hosts economically important oredeposits (Pejatoviç 1979). The zone, located in theeastern Black Sea region extending E–W along 350 kmand N–S along 60 km, is described Pontide metallogenicbelt (Akıncı 1980). In the region, VMS depositsaccompanying the Upper Cretaceous felsic volcanics arecommon (Çağatay & Boyle 1977; Leitch 1981; Schneideret al. 1988; Çağatay 1993; Tüysüz 2000; Akçay 2008)and potentially important in the Cu, Pb and Znproductions. These deposits have features similar to theKuroko-type deposits in Japan and commonly occurwithin intensely altered felsic volcanic rocks (Sato 1977;Leitch 1981; Urabe & Marumo 1991; Çağatay 1993;Antonovic et al. 1996; Barrett & MacLean 1999; Akçay& Moon 2001; Akçay 2008). The abandoned Kutlularmine (Sürmene, Trabzon), one of the largest volcanogenicmassive sulfide (VMS) deposit in Turkey, is located about4 km south of the Black Sea coastline and 14 km to theeast of Sürmene (Trabzon) in NE Turkey (Figure 1).

The mineralogy and lithogeochemistry of thehydrothermally altered volcanic rocks have beenextensively used to define hydrothermal alteration haloes.Many attempts have been made to define mineralogy,chemistry and chemical changes of hydrothermally alteredfootwall and hanging wall in several VMS deposits aroundthe world (e.g., Bryndzia et al. 1983; Urabe et al. 1983;MacLean & Kranidiotis 1987; Barriga & Fyfe 1988; Large1992; Barret et al. 1993a, b; Çağatay 1993; Çağatay &Eastoe 1995; Barret et al. 1996; Lentz & Goodfellow1996; Ohmoto 1996; Peter & Goodfellow 1996;Almodóvar et al. 1998; Leistel et al. 1998; Gibson et al.1999; Paulick & McPhie 1999; Sánchez-España et al.2000; Paulick et al. 2001; Akçay 2003, 2008). Thispaper presents the results of mineralogical andgeochemical studies of hydrothermal alteration zonesassociated with the Kutlular massive sulfide deposit in NETurkey.

Geological Setting

The eastern Pontides, located along the Alpinemetallogenic belt, is one of the best-preserved examplesof a palaeo-arc setting formed by subduction of theTethyan ocean crust from Jurassic to Miocene (Dixon &Pereira 1974; Şengör & Yılmaz 1981; Okay & Şahintürk1997). Although many authors are still disputing aboutthe polarity and timing of the subduction and formation

of the eastern Pontides (Şengör & Yılmaz 1981; Bektaş1987; Bektaş et al. 1998; Boztuğ et al. 2004, 2006,2007), it is known that subduction was completed bymiddle Eocene (Adamia et al. 1981; Okay & Şahintürk1997). The eastern Pontides straddle the North Anatoliantransform fault and display three major volcanic cycles ofLiassic, Late Cretaceous and Tertiary age. Volcanic rocksof Liassic age are transitional, those of Late Cretaceousages are subalkaline, and Eocene volcanic rocks arealkaline and subalkaline in character (Arslan et al. 1997,2007; Arslan & Aslan 2006). Volcanism in the regionbegan during the Liassic time with the formation of basicrocks in a rift environment (Tokel 1972; Schneider et al.1988; Arslan et al. 1997), developed on a Precambrian toPalaeozoic basement (Yılmaz 1972; Okay & Şahintürk1997; Topuz et al. 2001; Topuz 2002). Liassic volcanismcomprises of calcalkaline volcanic and volcanoclastics withlocally deposited sedimentary rocks (Arslan et al. 1997).These units are overlain by Dogger to Lower Cretaceousplatform carbonates. After the deposition of thecarbonate rocks, island arc volcanic activity began (Eğin etal. 1979). In the Late Cretaceous, early mafic rocks werefollowed by felsic rock series, and then by upper maficrocks. These rocks are composed of dacites and basaltswith calc-alkaline composition, and reflect the features ofthe arc volcanism (Tokel 1977). The Upper Cretaceousrocks host the volcanogenic massive sulphide (VMS)deposits in the region. The Kutlular and other VMSdeposits (e.g., Murgul, Lahanos and Çayeli) are located inthe intra-arc rift zone of the Pontide island arc.

Material and Methods

Eighty samples of mafic and felsic rocks of the Kutlulararea were selected for optical microscope, X-raydiffraction and lithogeochemical studies. Opticalmicroscope studies were carried out on lavas, pyroclasticsand partly altered rocks. Selected samples forgeochemical and X-ray diffraction (XRD) analyses wereground using an agate mortar and pestle. In order toobtain clay fractions (<2 μm), chemical treatments(Jackson 1956; Mehra & Jackson 1960; Kunze 1965)were carried out to remove carbonates, amorphous silicaand free Fe oxides. After that, clay fractions (<2 μm)were separated by sedimentation, followed bycentrifugation of the suspension after overnightdispersion in distilled water. More complete dispersion ofclay particles was achieved by ultrasonic treatment for

HYDROTHERMAL ALTERATION OF THE KUTLULAR DEPOSIT

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E. ABDİOĞLU & M. ARSLAN

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250İdrom T.

+ -

06 00001 06 00002 06 00003

45

000

2845

000

2945

000

30

b)

+

-+

+-

Sargana

D.

İdrom T.

Gökç

esu

Vall

ey

-Çalapetra

NN

200 m

rhyolite, rhyodacite

and their pyroclastics

dacite dyke

basalt, basaltic andesite

and their pyroclastics

(hanging-wall mafic volc.)

dacitic pyroclastics

(footwall volcanics)

formation

boundary

250

isohips

open pit

altered dolerite

dyke

dacite

basalt and its

pyroclastics

stream

fault+

-

UP

PE

RC

RE

TA

CE

OU

S

TURKEY

NAFZ

Fatsa

Ordu

Vakfıkebir Trabzon

Çayeli

Pazar

Arhavi BorçkaHopa

Murgul

Sürm

ene

OfYomra

Rize

MaçkaTonya

Espiye

Tirebolu

Giresun

Gölköy

B l a c k S e a

30 km

N

41

30

o, 37 30

o,

38 30o

,

39 30o

,

40 30o

,

41 30o

,

38o

39o

40o

41o

42o

İkizdere

G.hane

EA

FZ

Aeg

ean

Sea

Black Sea

circular structures (calderas, domes)

reverse faults

Mediterranean Sea

massive sulphide deposits(1) Cerattepe (Artvin)

(2) Murgul (Artvin)

(3) Madenli (Rize)

(4) Kutlular (Trabzon)

(5) Kanköy (Trabzon)

(6) Köprübaşı (Giresun)

(7) İsraildere (Giresun)

(8) Harköy (Giresun)

(9) Lahanos (Giresun)

97

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54

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2 Artvin1

6

granitoids

basic volcanics (alkaline province)

andesitic-basaltic volcanics

(calc-alkaline province)

clastic sedimentsPliocene

L. Cretaceous-

Eocene

Eocene-

Pliocene

Upper

Cretaceous

marl, clayey limestone, shale

sandstone, marl, reefal limestone

dacitic and rhyodacitic volcanics

basaltic, andesitic volcanics

Liassic-Lower

Cretaceous

undifferentiated lithologies

clayey-, cherty- and sandy limestone

basalt, andesite and dacite

Palaeozoic Gümüşhane Granitoid

EXPLANATION

a

b

40

30

o,

41

o

Kutlular

Gökçesu

Amar T.

Figure 1. (a) The simplified geological map of the eastern Pontides. The Kutlular and the other significant massivesulfide deposits are marked on the map (simplified from Güven 1993 and Akçay & Moon 2001). (b)Geological map of the Kutlular (Sürmene-Trabzon) area in NE Turkey. NAFZ– North Anatolian Fault zone;EAFZ– East Anatolian Fault Zone.

~15 min. XRD analyses were carried out using a RigakuDMAX 2200 and a Rigaku DMAXIIC X-ray diffractometre(Cu-Ka and Ni filter). Semi-quantitative mineralabundances were identified using the mineral intensityfactors according to an external standard method(Brindley 1980). Oriented clay fractions were analyzed inthe untreated state (N), after ethylene glycolation (EG; 60°C, 16 h) and after heating (H; 300 and 550 °C).

Whole rock and clay fraction samples were analyzedfor major, trace and rare earth element (REE) analysis.Chemical analyses of whole-rock and clay fractions werecarried out by ICP-AES and ICP-MS at ACME AnalyticalLaboratories Ltd. (Canada). Detection limits range from0.01 to 0.1 wt% for major elements, 0.1 to 5 ppm fortrace elements and 0.01 to 0.5 ppm for the REE.

Results

Local Geology and Petrography

In the Kutlular area, Upper Cretaceous mafic, felsicvolcanics and subvolcanic rocks crop out. The oldest rocksof the study area are formed by basalt and its pyroclasticderivatives. This unit is overlain by barren dacite andfootwall dacite, respectively. The basalt, basaltic andesiteand their pyroclastics as hanging-wall mafic rocks overlythe footwall rocks. The altered dolerite and dacite dykescut all the units.

The Kutlular massive sulphide deposit has generallymassive, stringer and disseminated ore. It consists ofthree primary seafloor mineral assemblages and asupergene assemblage. The first primary association(black ore) includes mainly sphalerite, pyrite, galena, andtetrahedrite-tennantite. The second association (yellowore) contains mainly of chalcopyrite, pyrite and lessersphalerite and tetrahedrite-tennantite. The last one,pyritic ore, comprises pyrite, rare chalcopyrite andtetrahedrite-tennantite. The supergene mineralizationconsists of mainly covellite, chalcocite, bornite, malachiteand azurite. The Kutlular mine has 1.26 Mt ore, 0.76 Mt(with an average grade of 2.4% Cu, 1.5% Zn and 0.04%Pb) of which was mined between 1986 and August 1992(Çağatay & Eastoe 1995). According to Yıldız (1988), theweighted average content of Cu was 2.83 %. The massivesulfide lens was underlain mainly by dacitic tuff andcovered by dacitic-pumiceous tuffs, dacitic breccias andbasalt-basaltic andesite lavas that intruded by altereddolerite dyke. Before the mining activities, fine-grained

gypsum occurrences could be observed as small pockets inthe hanging wall pyroclastic rocks (Çağatay & Eastoe1995).

Lower Units. Here the mafic volcanics, consisting ofaltered basalt and pyroclastics of similar composition,make up the basement rocks of the area. These rocks arewell exposed along Gökçesu valley. The basaltic rocks aredark grey and blackish in colour and show microliticporphyritic texture. The plagioclase is the mainconstituent of the rock. The groundmass consists mainlyof plagioclase microlites, chlorite and opaque phases. Therocks are highly altered and secondary pyrite and lesseramount of chlorite, quartz, zeolite and clay minerals arealso observed.

The lower dacites, mainly the dacites and to lesserextent dacitic pyroclastics are exposed along Gökçesuvalley and İdrom Tepe. These rocks overlie the basementrocks and underlie the footwall dacitic rocks. Grey,greenish grey and white coloured barren dacite includeslarge quartz and feldspar crystals up to 3 mm as well asdisseminated pyrite. The dacite exhibits porphyritictexture and contains quartz and plagioclase phenocrysts.Highly chloritized biotite pheno- and micro-crystals anddisseminated opaques are also observed. The groundmassis formed by secondary quartz, albite, sericite, chloriteand clay minerals.

Footwall Rocks. The footwall rocks are variablyhydrothermally altered and the intensity of alterationincreases with proximity to the massive sulfide body. Thefootwall dacite is generally in the form of pyroclasticswith only minor lavas, and is usually hydrothermallyaltered and surficially weathered. The volcanic brecciashave angular to rounded pyroclasts, typically 7–20 cm.The pyroclasts are commonly vesicular and cemented withash. In hand specimen, the broken surfaces of the daciticrocks are beige, greyish white and altered surface is grey,light yellow, light brown and creamy white in colour. Theintensity of surficial weathering and hydrothermalalteration affects the macroscopic view of the footwalldacite; the highly clayey-altered part of the rocks is verysoft and whitish in colour while silicified parts are veryhard and include visible disseminated pyrite of variablesize.

Dacitic tuffs are characterized by abundant quartzpheno- and micro-crystal fragments in variable size,feldspar, altered pumice, dacitic lithic fragments, and


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abundant amount of opaques, in a fine-grained matrixwith Fe-oxide pigmentation (Figure 2a, b, e). Feldsparmicro- and pheno-crystal fragments are partly silicified,argillizated and transformed into kaolinite and quartz(Figure 2d). Sericite occurs as replacement of plagioclase,mica and other aluminosilicate minerals, and asreplacement of the groundmass, especially volcanic glass(Figure 2a, b). A quartz-sericite-pyrite mineralassemblage occurs mainly in the footwall rocks of the orelens, as an inner alteration zone enveloping a core zone ofsilicification in the footwall. Chlorite, quartz, sericite andvitric fragments are other constituents of the rocks(Figure 2c–f). Pyrite is always present as disseminations(Figure 2f) and, to a lesser extent, as discontinuousveinlets within these rocks. Vuggy quartz is characterizedby fine-grained quartz with abundant open spaces thatare partly filled by clays and rarely other alterationminerals. Vugs typically are formed by dissolution ofphenocrysts and vitric fragments of the pyroclastics in thedacitic rocks and are lined by quartz and pyrite. In manycases, the sulfides are oxidized, resulting in extensivelimonite coatings around vugs. Quartz forms a densemosaic texture.

The dacites generally show porphyritic and glassytextures. They contain euhedral and subhedral quartzmicrocrysts and phenocrysts. Plagioclase microlites andphenocrysts are partly silicified and sericitized. Thegroundmass includes secondary quartz, albite, chloriteand clay minerals. Skeletal ferromagnesian minerals areintensely fractured and occasionally chloritized andsilicified. Open spaces such as vesicles, vugs and fracturesare filled with chlorite.

Hanging-Wall Mafic Volcanics. In the studied area,hanging-wall mafic volcanics are well exposed above thefootwall rocks and are composed mainly of basalt, basalticandesite and their pyroclastic equivalents. They are bestseen in the open pit area and surroundings. Their colourranges from black to dark grey and locally reddish andyellowish black. Basalt and basaltic andesites exhibitphysical weathering such as exfoliation but generally havewell-developed columnar jointing. The unit locally showssilicification, chloritization, epidotization, argillization andis cut by quartz and calcite veinlets. The lower part of thelavas consists of ellipsoidal-circular shaped volatile spaces,whose diameter changes from 0.5 to 3 cm, partlyembedded by quartz (in symmetrical), calcite and zeolite(e.g., laumontite, stilbite and analcime) infillings.

Basalt and basaltic andesite samples exhibit fluidal,microlitic, porphyritic, and vesicular and rarely aphanitictextures. Plagioclase (especially oligoclase and andesine) isthe main rock-forming mineral, sometimes arranged sub-parallel to flow direction of lavas and found as bothmicrolite and euhedral or subhedral phenocrysts. In somesamples, plagioclase has been partly replaced by albite,calcite and zeolite (e.g., heulandite and laumontite).Albitization and carbonitization of primary plagioclasealso occurs as reaction rims or along crystal fractures(Figure 3a–c). Minor amounts of epidote are generallyfound as infilling, surrounded by zeolite and calcite andsometimes as the patchy replacement of plagioclase(Figure 3b). Skeletal augite and olivine are rarely seen andmay be intensely fractured, occasionally chloritized andlined by opaque rims (Figure 3d). Subhedral and euhedralopaque grains are always present. The groundmass iscommonly altered to calcite and zeolite or partially tochlorite and clay minerals (smectite and illite). Chloritesare determined as infillings and replacement of glass ingroundmass and glassy inclusions on sieve texturedplagioclase (Figure 3c, d). The degree of alterationincreases with fracture intensity, the presence of glassymatrix and distance to the massive ore lens.

Altered Dolerite Dyke. It is exposed in the Kutlular openpit area, northeast and south of the ore lens. Its colourchanges from yellowish black to dark yellowish grey andplagioclase phenocrysts are described in naked eye andexhibit well-developed columnar jointing.

The altered dolerite dyke shows intersertal, poikiliticand ophitic textures. Plagioclases (labradorite) are themain constituents of the rock and are partly albitized,chloritized and sericitized. The angular intersticesbetween plagioclase grains are occupied by grains ofaugite and pigeonite. Secondary minerals are representedby chlorite and calcite as vesicle infillings and alterationproducts of the primary minerals. Opaque minerals areseen in the micro-vesicles and voids of the rock.

Clay Mineralogy and Chemistry

Clay mineralogy of altered volcanic rocks was identified indetail by XRD studies. It should be pointed out here thatthe roentgenographically determined illite corresponds tooptically determined sericite in these types of rocks (e.g.,Srodon & Eberl 1984). Lower dacites include smectite,illite, kaolinite, and interstratified smectite/chlorite in


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relative abundances. Footwall dacite consists mainly ofNa-Ca smectite, illite, regular and irregular interstratifiedillite/smectite, interstratified chlorite/smectite and rarelykaolin group minerals (kaolinite and halloysite). Theabundances of these minerals change in respect todistance to the ore body. The ore is enveloped by illite andsilica minerals. In the footwall, this zone is transitional to

illite/smectite and than smectite zone, respectively. Smallpockets of the kaolin group minerals are also observed inthe smectite zone. The outer zone mainly consists ofchlorite and interstratified minerals. Hanging-wall maficrocks are generally chloritized and partly albitized.Common clay mineralogy in this rock type is chlorite,illite, smectite, irregular interstratified chlorite/smectite.


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0.6 mm

0.6 mm

0.6 mm

0.6 mm

0.6 mm

0.6 mm

a b

c d

e f

Q

QQ

Q

Q

SeSe

Se

Se

Se

Q Q

Op

Op

Op

OpOp

Op

Op

OpOp

Op

Q

Q

Q

Q

Q

F

V

V

FF

Fe Fe

Fe

Fe

Ar+Si

Ar+Si

Ar+Si

Se+Si

Ar+Si

Ar+Si

Ar+Si

Figure 2. Photomicrographs of footwall dacites under crossed polars: (a) and (b) sericitization and silicification ofvolcanic glass in dacitic vitric-crystal tuff. Glass shards are replaced by sericite and quartz; (c)argillization and silicification of volcanic glass in vitric tuff; (d) quartz-kaolinite replacement of feldspars,silicification and argillization of groundmass; (e) pigmentation of Fe-oxides and primary embayed quartzlined by secondary quartz crystals in silicified and argillizated groundmass; (f) silica and clay flooding ofmatrix and quartz-filled vesicles in the immediate footwall. Abbreviations: Ar– argillization; Fe– ironoxide; F– feldspar (ortoclase); Se– sericitization, Si– silicification; Q– quartz, Op– opaque, V– void.

Similar clay minerals can be observed in altered doleritedyke, and are composed of chlorite illite/smectite (Figure4a, b).

Based on clay mineralogy, hydrothermal alterationzones are well developed and represented by silicification-pyrite-illite zone, illite-silicification zone, illite/smectite-silicification zone and smectite zone accompanyingkaolinite and halloysite in the footwall rocks, andadditionally, chlorite zone in the hanging-wall rocks. Inthe hanging-wall rocks, zeolite facies minerals such asheulandite, analcime, laumontite and calcite were alsodetermined.

Major element concentrations of purified smectite,kaolinite and illite (<2 μm) and their structural formulaecalculated on the basis of 22 oxygen atoms for smectiteand illite, and 14 oxygen atoms for kaolinite (Weaver &Pollard 1973; Newman & Brown 1987) are given inTables 1 and 2. The dioctahedral smectites are rich in Al(22.88 and 23.85 wt% Al2O3). The K2O content is 0.07–

0.17 wt% and K as interlayer cation is 0.01–0.03 perunit formulae. These values may not be consistent withgeneral smectite compositions. Interlayer regions areoccupied by Ca, Na and K. Octahedral charge of smectitesrange from 0.36 to 0.45 and tetrahedral charge from0.06 to 0.14 and tetrahedral/octahedral ratios <1. Forthis reason, this smectites are classified asmontmorillonite (Güven 1988).

The structural formula of kaolinite was calculatedfrom chemical analyses of the clay fractions extractedfrom sample K40, as given in Table 1. Molar SiO2/Al2O3

ratio is 1.17, total Fe2O3total content is 1.04 wt%, andMgO content is 1.90 wt% (Tables 1 & 2). Generally it iswell known that analysis of an ideal kaolinite does notcontain such an amount of iron and magnesium thereforethe iron content of kaolinites has been subject of somediscussion (Herbillon et al. 1976; Rengasamy 1976;Angel & Vincent 1978; Mestdagh et al. 1980; Cuttler1981; Komusinski et al. 1981). In the studied kaolinite-


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0.6 mm

0.6 mm

0.6 mm

0.6 mm

a b

c d

He

HeHe

Pl

Pl Ep

EpCa

Ca

Ca

Ca

Ca

Op

Op

Op

Ol

Op

Ch

ChCh

Ch

Ch

V

Ch

Pl

Pl

Pl

Pl

Px

Ch

Ch

Pl

Figure 3. Photomicrographs of hanging wall basalts under crossed polars: (a) amygdaloidal zeolite (heulandite)filling; (b) calcite and epidote formed on plagioclase; (c) Sieve texture in plagioclase and formation ofcalcite and chlorite on Ca-rich plagioclase; (d) skeletal pyroxene and olivine partly converted to chloriteand opaque. Abbreviations: Ca– calcite; Ch– chlorite, Ep– epidote; He– heulandite, Pl– plagioclase, Px–pyroxene; Ol– olivine, V– void.

rich samples, SEM investigations suggest that amorphousiron coatings are common around the kaolinite fibers andparticles and kaolinite are generally derived from thevolcanic glass fragments. So that, excess iron content inthe chemical analysis of the studied kaolinite may resultfrom iron coatings, and excess magnesium content fromthe partly dissolved glass that may not be successfully

removed with chemical treatments. However, high qualityXRD studies (normal, EG solvated, heated) did not showany type of intercalations or impurities. It is suggestedthat Fe3+ and Mg2+ might played an important role withinthe octahedral layers, replacing some of the Al.

K2O contents of the illites and illite/smectites rangefrom 6.15 to 7.56 wt% and 5.17 to 5.96 wt%, and the


146

+ -

20 m

NN

open pit area

kaolinite and halloysite

albite+chlorite

carbonate+chlorite

altered dolerite dyke silicification-pyrite-illite zone

hanging-wall mafic

volcanics

footwall felsic volcanis

ore zone

.

illite-silicification zone

illite/smectite-silification zone

smectite zone

chlorite zone

Not scaled

increasing Ishikawa index

increasing K,

decreasing Na and Ca

increasing CCPI

+-

fault

a

b

Figure 4. (a) Alteration map of the Kutlular VMS; (b) model of alteration associatedwith the Kutlular VMS.


147

Table 1. Major element (wt%) compositions of clay fraction from the Kutlular area (Sürmene, Trabzon), NE Turkey.

Sample No KP3-3 KP3-5 K40 K33 KP3 KP2a KP2-1 KP4-7 KP3-8 KP1-11 KP1-11a KP3-2Mineralogy Na-Ca S Ca-S kaolinite illite illite illite/ illite/ Ch/S, S Ca-S, Ch/illite, Ch/illite, Ch/S,

smectite smectite illite. S, Ch S, Ch Na-S, illitekaolinite

SiO2 62.07 62.62 44.55 47.73 49.45 54.31 49.73 48.95 58.04 58.77 62.82 50.05Al2O3 23.85 22.88 37.94 31.53 32.58 27.18 25.94 23.50 16.97 19.19 16.96 26.17Fe2O3

total 1.63 2.84 1.04 0.67 2.51 1.50 3.83 3.68 7.66 1.21 1.14 3.23MgO 2.09 1.86 1.90 1.28 1.38 1.07 0.67 0.63 2.14 1.28 1.20 0.63CaO 1.12 1.040 0.08 0.77 1.20 0.09 0.06 0.11 0.92 0.89 0.77 0.07Na2O 1.03 0.51 0.61 0.15 1.15 1.07 0.10 1.03 6.00 4.20 2.88 0.09K2O 0.17 0.07 0.04 7.56 6.15 5.17 5.96 3.81 0.350 0.460 0.590 6.060TiO2 0.06 0.06 0.53 2.56 0.640 0.70 0.39 0.74 0.480 0.600 0.590 0.570P2O5 0.03 0.04 0.09 0.69 0.000 0.02 0.04 0.02 0.06 0.02 0.02 0.04MnO 0.01 0.01 0.13 0.01 0.030 0.01 0.01 0.04 0.07 0.02 0.02 0.01BaO 0.079 0.002 0.053 0.119 0.000 0.106 0.048 0.034 0.027 0.010 0.018 0.050Cr2O3 0.007 0.008 0.013 0.002 <0.01 0.002 0.003 0.001 0.002 0.002 0.002 0.002LOI 7.89 8.12 14.10 6.50 5.30 8.70 13.10 16.40 7.10 13.20 13.00 12.90Sum 100.04 100.06 101.08 99.57 100.39 99.93 99.88 98.95 99.82 99.85 100.01 99.87

LOI, represents loss on ignition; Fe2O3total stands for total iron oxide as ferric iron.(Abbreviations: Na-Ca-S, Na-Ca smectite; Ca-S, Ca-smectite; Ch, chlorite; S, smectite)

Table 2. Structural formulae of the smectites, illite, illite/smectite and kaolinite of the Kutlular(Sürmene, Trabzon) area (Abbreviations: Na-Ca-S, Na-Ca smectite; Ca-S, Ca-smectite).

Sample No KP3-3 KP3-5 K40 K33 KP3 KP2a KP2-1

Mineralogy Na-Ca-S Ca-S kaolinite illite illite illite/smectite illite/smectite

TetrahedralSi 7.8601 7.9418 3.8521 6.3914 6.4488 7.2188 7.0466IVAl 0.1399 0.0582 0.1479 1.6086 1.5512 0.7812 0.9534Sum 8.0000 8.0000 4.0000 8.0000 8.0000 8.0000 8.0000

OctahedralVIAl 3.4196 3.3618 3.7185 3.3674 3.4563 3.4767 3.3786Ti 0.0057 0.0057 0.0345 0.2578 0.0628 0.0700 0.0416Fe3+ 0.1553 0.2710 0.0677 0.0675 0.2463 0.1500 0.4084Mg 0.3945 0.3516 0.2449 0.2555 0.2682 0.2120 0.1415Cr 0.0004 0.0004 0.0004 0.0001 0.0000 0.0001 0.0002P 0.0016 0.0021 0.0033 0.0391 0.0000 0.0011 0.0000Ba 0.0039 0.0001 0.0018 0.0063 0.0000 0.0055 0.0027Sum 3.9810 3.9928 4.0000 3.9936 4.0000 3.9154 3.9729

InterlayerCa 0.1520 0.1413 0.0074 0.1105 0.1677 0.0128 0.0091Na 0.2529 0.1254 0.1023 0.0389 0.2908 0.2758 0.0275K 0.0275 0.0113 0.0044 1.2914 1.0231 0.8766 1.0773 Mg 0.0000 0.0000 0.0710 0.0000 0.0336 0.0000 0.0000Sum 0.4323 0.2781 0.1141 1.4408 1.4815 1.1652 1.1139Si/Al 2.2082 2.3222 0.9963 1.2844 1.2878 1.6954 1.6266TC 0.1399 0.0582 0.1479 1.6086 1.5512 0.7812 0.9534OC 0.4465 0.3637 -0.0077 -0.0553 0.1046 0.3991 0.1836TOT 0.5864 0.4219 0.1402 1.5535 1.6558 1.1803 1.1370IC -0.5843 -0.4194 -0.2635 -1.5513 -1.7165 -1.1780 -1.1230

TC, tetrahedral charge; OC, octahedral charge; TOT, Total charge (octahedral charge + tetrahedral charge); IC, interlayer charge

value of K+ are from 1.02 to 1.29 and from 0.88 to 1.08moles in formula unit, respectively. CaO contents of theillites and illite/smectite are from 0.77 to 1.20 wt% and0.06 to 0.09 wt%. Interlayer region is occupied by K+,Ca2+ and Na+ (Tables 1 & 2).

Whole Rock Geochemistry

Formation of the VMS results in intense alteration anddevelopment of alteration haloes around the ore body.Due to strong hydrothermal alteration of footwall andhanging-wall rocks, many of the analyzed elements cannot be used for the chemical discrimination of the rocktypes. However, some of the elements in the footwall andhanging wall rocks are implied to behave immobile (e.g.,Ti, Al, Zr) during the generation of ore (MacLean &Kranidiotis 1987; MacLean 1990; Barret et al. 1993a, b;Shriver & MacLean 1993; Barret & MacLean 1994). Mostof the major and trace elements are not useful forchemical discrimination of the Kutlular volcanics due tothe intense hydrothermal alteration. For these reasons,the immobile element (Zr, Ti, Nb, Yr) chemicaldiscrimination diagram of Winchester & Floyd (1977)revised by Pearce (1996) was used (Figure 5; Tables 3 &4). The lower dacite falls into the andesite-basalticandesite field, probably due to the slight enrichment ofthe Y. The footwall dacites scatter on andesite/basalt andrhyolite/dacite fields, probably due to the intensehydrothermal alteration. The hanging-wall rocks fall intobasalt, andesite-basaltic andesite and occasionally rhyolite-dacite fields. While interpreting these scattering, it shouldbe taken into account that Y is slightly mobile than Nbwhereas Ti and Al are highly immobile elements (MacLean& Kranidiotis 1987; MacLean 1990; Barrett & MacLean1991; Barrett 1992; Shriver & MacLean 1993; Hill et al.2000). Geochemical affinities of the volcanic rocks aredetermined by using immobile element binary plot of La-Yb and Zr-Y (Figure 6). The volcanics show similaraffinity in both diagrams and are generally transitionalbetween tholeiitic and calc-alkaline in character.

The trace elements patterns of the samples showconsiderable LILE enrichment (K, Rb, Ba and Th) anddepletion in Sr and Ti relative to N-MORB (Figure 7).Normalized trace element pattern may be represented bythat of island-arc calc-alkaline volcanics (Pearce 1983).Chondrite-normalized REE patterns of the footwall rocksshow marked HREE enrichment, a feature which is

common in felsic rocks formed in evolved island arcs(Almodóvar et al. 1998). The footwall and hanging-wallrocks have negative and positive Eu and Ce anomalies,respectively, indicating different degree of hydrothermalalteration resulted of interaction with sulphide-sulphateore forming fluids (Shikazono 2003). Although thenegative Eu anomalies in the rocks may reflect plagioclasefractionation in the evolution of the volcanics, it should bekept in mind that Eu content could be diminished due tothe hydrothermal breakdown of plagioclase (Shikazono2003; Figure 8).

Alteration Indices

Ishikawa alteration index (AI) and the chlorite-carbonate-pyrite index (CCPI) track the chemical and mineralogicalchanges associated with hydrothermal alteration(Ishikawa et al. 1976; Large et al. 2001). The Ishikawaindex (AI=[100*(K2O+MgO)]/(K2O+MgO+Na2O+CaO))was defined by Ishikawa et al. (1976) to quantify theintensity of sericite and chlorite alteration that occurs inthe footwall volcanic rocks proximal to Kuroko-type VMSdeposits. Large et al. (2001) imply that the index variesfrom values of 20 about 60 for unaltered rocks andbetween 50 and 100 for hydrothermally altered rocks,with an AI= 100 representing complete replacement offeldspar and glass by sericite and/or chlorite. Thecalculated AI values of the footwall dacites and the lowerdacites from the Kutlular mine range from 0.91 to 98.39and from 16.25 to 94.57, respectively. AI values ofhanging mafic volcanics and altered dolerite dyke are 2.38


148

0.01 0.1 1 10 100Nb/Y

0.01

0.1

1

Zr/

TiO

2*0

.0001

andesite-basalticandesite

phonolite

trachyte

foidite

trachy-and.

alkalibasalt

basalt

rhyolite-dacite tephri-

phonolite

0.002

altered dolerite dykehanging-wall mafic volcanicsfootwall rockslower dacites

Figure 5. Discrimination of the Kutlular area volcanics using a Nb/Y-Zr/TiO2 immobile element diagram of Pearce (1996) (afterWinchester & Floyd 1977).


149

Tabl

e 3.

M

ajor

(w

t%)

and

trac

e el

emen

t (p

pm)

com

posi

tions

of

the

foot

wal

l and

the

low

er d

acite

fro

m t

he K

utlu

lar

(Sür

men

e, T

rabz

on)

min

e. A

bbre

viat

ions

: AI

– Is

hika

wa

alte

ratio

n in

dex,

CCPI

– Ch

lori

te-c

arbo

nate

-pyr

ite in

dex.

low

er d

acite

sfo

otw

all v

olca

nics

K-2

6K

-28

K-2

9K

P1-1

KP1

-1*

KP1

-2K

P1-3

KP1

-4K

P1-5

KP1

-7K

P1-8

KP1

-9K

P1-1

0K

P1-1

1K

P1-1

2K

40

SiO

267

.70

70.9

364

.72

61.7

347

.97

50.3

056

.58

74.3

051

.83

72.8

492

.37

43.7

520

.28

50.9

757

.63

37.7

1Al

2O3

17.9

813

.73

17.4

418

.26

21.8

225

.46

21.4

42.

7623

.92

9.26

3.08

12.7

22.

9225

.02

18.3

823

.77

Fe2O

3tota

l4.

054.

475.

554.

9610

.97

3.27

3.70

16.9

83.

151.

690.

8317

.84

38.3

42.

524.

7612

.81

MgO

0.30

0.98

0.56

0.56

1.72

0.88

1.21

0.05

1.05

0.04

0.11

0.91

0.28

0.93

1.44

1.71

CaO

0.01

0.23

0.02

0.20

0.07

0.08

0.03

0.11

0.05

0.29

0.12

0.08

1.53

0.10

0.07

0.19

Na 2

O0.

095.

130.

042.

460.

030.

900.

190.

100.

453.

420.

250.

330.

060.

500.

110.

01K

2O1.

440.

060.

071.

094.

381.

973.

060.

042.

910.

110.

162.

240.

262.

224.

16Ti

O2

0.39

0.39

0.49

0.43

0.28

0.56

0.32

0.19

0.32

2.32

0.08

0.31

0.08

0.32

0.32

0.81

P 2O

50.

020.

020.

030.

050.

040.

040.

040.

140.

040.

090.

010.

020.

010.

060.

010.

10M

nO0.

010.

100.

130.

020.

050.

020.

030.

220.

040.

020.

010.

020.

010.

040.

030.

26LO

I8.

003.

9010

.90

10.2

012

.50

16.4

013

.20

5.00

16.1

09.

603.

0021

.60

36.1

017

.10

12.0

021

.70

Sum

99.9

999

.94

99.9

599

.96

99.8

399

.88

99.8

099

.89

99.8

699

.68

100.

0299

.82

99.8

799

.78

98.9

199

.07

FeO

tota

l3.

644.

024.

994.

469.

872.

943.

3315

.28

2.83

1.52

0.75

16.0

534

.50

2.27

4.28

11.5

3

Cu5.

1087

.90

334.

9010

7.90

466.

2011

6.00

161.

6019

1.30

150.

9080

.30

73.6

053

.00

8.10

160.

1035

.30

4594

.80

Pb6.

002.

702.

8050

.60

18.0

089

.30

66.8

076

5.80

106.

8013

9.90

17.5

059

.60

10.7

015

5.10

15.3

025

.60

Zn8.

0036

1.00

164.

0027

.00

187.

0021

.00

43.0

025

.00

35.0

06.

0010

.00

24.0

037

.00

33.0

093

.00

1990

.00

As1.

903.

103.

6056

.90

10.6

013

3.60

131.

7031

2.20

139.

4020

4.40

14.3

038

7.20

260.

2013

9.70

62.5

07.

40Ba

239.

0017

5.10

111.

5033

3.50

629.

2086

1.00

1491

.70

352.

6077

7.60

2254

.40

154.

3053

8.00

1341

.90

1299

.60

8050

.50

787.

50Y

37.2

066

.90

47.5

025

.20

32.0

031

.10

27.9

023

.10

44.4

016

.90

4.90

23.9

03.

6044

.20

26.4

018

.00

Zr23

4.80

136.

8016

7.40

143.

1025

3.20

179.

4022

7.70

117.

3025

7.30

161.

2036

.40

149.

8059

.00

247.

6022

6.50

25.1

0N

b6.

502.

202.

902.

504.

203.

103.

702.

605.

103.

801.

002.

400.

904.

203.

500.

50R

b19

.20

2.30

2.90

25.8

094

.70

36.1

057

.40

1.10

58.2

03.

004.

3035

.40

4.70

45.1

068

.40

1.00

Sr8.

6054

.90

4.50

91.7

06.

9046

.10

22.1

036

.30

28.2

013

1.10

33.5

038

.50

20.2

034

.20

34.3

011

.30

Th5.

802.

302.

601.

603.

801.

903.

001.

603.

702.

100.

902.

000.

904.

502.

500.

40U

1.70

0.40

0.60

2.10

1.00

3.10

1.20

0.90

1.50

5.50

0.50

4.50

3.10

1.90

2.50

0.30

La2.

2010

.20

13.6

06.

204.

701.

201.

2021

.90

0.70

1.40

0.70

1.10

1.50

0.80

9.60

4.10

Ce14

.00

16.0

021

.30

11.7

013

.80

3.80

3.70

47.5

02.

803.

002.

104.

205.

102.

8019

.20

7.00

Pr0.

704.

415.

171.

161.

730.

370.

315.

180.

240.

320.

240.

520.

730.

282.

201.

01N

d3.

1019

.80

23.4

04.

107.

402.

502.

7015

.50

1.70

1.20

1.10

3.00

3.30

1.80

9.30

4.80

Sm1.

306.

106.

301.

403.

100.

802.

104.

301.

000.

500.

401.

101.

100.

803.

101.

00Eu

0.26

1.55

1.63

0.28

0.90

0.25

0.48

1.03

0.38

0.07

0.13

0.30

0.41

0.26

0.90

0.42

Gd

2.54

9.03

7.08

1.88

5.32

2.19

4.36

4.04

2.81

1.21

0.57

2.38

1.34

2.77

4.04

1.86

Tb0.

741.

491.

230.

551.

100.

530.

750.

730.

930.

280.

110.

670.

130.

810.

780.

32D

y5.

2910

.10

7.93

3.98

6.31

4.31

4.80

5.34

6.17

2.09

0.61

3.90

0.65

5.61

5.51

2.27

Ho

1.32

2.13

1.75

0.93

1.34

1.06

0.97

1.15

1.57

0.59

0.16

0.83

0.13

1.49

1.11

0.60

Er4.

326.

145.

022.

953.

733.

442.

833.

574.

711.

950.

512.

820.

444.

963.

691.

56Tm

0.79

1.07

0.88

0.60

0.67

0.68

0.52

0.60

0.79

0.34

0.09

0.53

0.07

0.77

0.67

0.22

Yb5.

346.

985.

103.

814.

194.

893.

383.

925.

002.

220.

683.

430.

374.

924.

271.

59Lu

0.80

1.02

0.85

0.66

0.67

0.72

0.54

0.66

0.81

0.38

0.11

0.57

0.07

0.84

0.74

0.27

Nb/

Y0.

170.

030.

060.

100.

130.

100.

130.

110.

110.

220.

200.

100.

250.

100.

130.

03Zr

/Y6.

312.

043.

525.

687.

915.

778.

165.

085.

809.

547.

436.

2716

.39

5.60

8.58

1.39

Zr/N

b36

.12

62.1

857

.72

57.2

460

.29

57.8

761

.54

45.1

250

.45

42.4

236

.40

62.4

265

.56

58.9

564

.71

50.2

0AI

94.5

716

.25

91.3

038

.28

98.3

974

.41

95.1

030

.00

88.7

93.

8942

.19

88.4

825

.35

84.0

096

.89

89.5

3CC

PI72

.05

49.0

898

.06

58.5

972

.44

57.1

258

.28

99.0

953

.62

30.6

667

.64

86.8

499

.09

54.0

357

.27

99.9

2La

/Yb

0.41

1.46

2.67

1.63

1.12

0.25

0.36

5.59

0.14

0.63

1.03

0.32

4.05

0.16

2.25

2.58

LOI i

s lo

ss o

n ig

nitio

n, F

eOto

tal =

0.8

998*

Fe2O

3tota

l(R

agla

nd 1

989)

.


150

Tabl

e 3.

(Con

tinue

d)

foot

wal

l vol

cani

csK

P2-1

KP2

-2K

P2-4

KP3

-1K

P3-2

KP3

-3K

P3-4

KP3

-5K

P4-1

KP4

-2K

P4-3

KP4

-5K

-13

K33

K34

K-3

7

SiO

282

.24

73.9

579

.66

79.6

881

.76

88.6

280

.95

85.1

958

.71

72.7

174

.65

83.3

374

.99

45.0

484

.27

88.9

7Al

2O3

7.85

4.89

10.7

510

.68

5.66

3.82

8.09

3.52

14.9

011

.98

10.9

25.

6910

.52

18.7

76.

996.

59Fe

2O3to

tal

3.22

10.6

80.

480.

714.

631.

093.

083.

019.

302.

482.

731.

660.

6415

.17

2.71

0.18

MgO

0.24

0.27

0.39

0.39

0.30

0.05

0.11

0.05

0.49

0.69

0.19

0.30

0.01

0.77

0.27

0.24

CaO

0.05

0.12

0.29

0.16

0.12

0.09

0.05

0.07

0.03

0.70

0.35

0.08

0.14

0.34

0.09

0.01

Na 2

O0.

040.

020.

040.

030.

020.

040.

020.

020.

082.

420.

050.

075.

330.

100.

040.

04K

2O1.

891.

182.

002.

111.

280.

131.

630.

063.

460.

892.

021.

450.

045.

251.

891.

68Ti

O2

0.12

0.09

0.21

0.18

0.09

0.09

0.15

0.07

0.45

0.33

0.32

0.39

3.27

1.77

0.12

0.12

P 2O

50.

020.

010.

010.

020.

010.

020.

020.

020.

020.

060.

020.

140.

190.

300.

010.

01M

nO0.

010.

010.

010.

010.

010.

010.

010.

010.

010.

010.

010.

010.

010.

010.

010.

01LO

I4.

208.

706.

105.

906.

004.

905.

805.

5012

.50

7.60

7.70

6.60

4.70

11.2

03.

302.

20Su

m99

.88

99.9

299

.94

99.8

799

.88

98.8

699

.91

97.5

299

.95

99.8

724

.31

99.7

299

.84

98.7

299

.70

100.

05Fe

Oto

tal

2.90

9.61

0.43

0.64

4.17

0.98

2.77

2.71

8.37

2.23

2.46

1.49

0.58

13.6

52.

440.

16

Cu53

9.10

114.

505.

506.

6043

5.70

112.

4020

.40

297.

6022

6.50

33.4

039

.60

201.

4029

.60

516.

5011

32.9

03.

60Pb

12.8

028

.20

79.1

056

5.10

37.6

035

.10

43.6

085

.80

12.2

028

.90

38.5

015

43.1

013

16.8

012

8.90

72.8

08.

10Zn

68.0

067

.00

18.0

036

.00

139.

0091

77.0

031

0.00

>10

000

58.0

022

7.00

79.0

081

.00

3.00

663.

0016

7.00

2.00

As18

.30

157.

3025

.70

55.3

016

9.20

52.7

011

2.50

98.5

059

.50

53.4

081

.30

19.0

010

8.10

130.

9066

.90

145.

60Ba

171.

6088

.40

160.

1018

3.50

141.

9030

2.40

74.8

029

.60

251.

1011

9.00

173.

1027

9.70

1438

.10

774.

9021

3.00

144.

60Y

16.7

013

.20

19.2

024

.90

12.6

011

.80

18.4

012

.10

24.6

028

.40

18.0

029

.90

11.2

024

.70

16.4

029

.30

Zr75

.70

53.8

010

9.20

126.

2057

.10

47.7

085

.20

44.1

013

6.30

106.

6010

3.70

128.

2016

2.80

74.2

082

.10

96.8

0N

b1.

500.

901.

802.

401.

101.

301.

601.

002.

501.

702.

002.

303.

902.

201.

301.

60R

b20

.10

18.4

020

.30

22.7

018

.60

1.30

12.5

00.

6038

.00

11.2

018

.80

16.8

00.

7079

.40

24.5

022

.40

Sr4.

406.

2010

.10

14.1

06.

809.

002.

906.

304.

3077

.90

8.40

86.8

073

.70

5.10

3.00

3.30

Th0.

800.

701.

201.

800.

800.

901.

600.

701.

702.

201.

001.

901.

300.

701.

301.

00U

0.30

0.30

0.60

0.60

0.40

0.40

0.50

0.20

0.70

0.30

0.50

1.20

7.30

1.00

2.10

0.40

La6.

102.

104.

407.

601.

705.

907.

209.

006.

506.

005.

5033

.40

4.30

2.40

4.80

2.50

Ce13

.20

2.90

9.60

17.2

03.

3010

.20

14.1

015

.00

16.7

015

.40

14.2

080

.40

7.20

8.50

10.8

06.

60Pr

1.77

0.40

1.29

2.10

0.45

1.49

1.86

2.14

2.34

2.33

2.06

10.9

10.

711.

501.

730.

93N

d6.

501.

804.

809.

901.

805.

807.

909.

008.

0011

.20

9.00

46.4

02.

307.

506.

704.

10Sm

2.50

0.70

1.50

2.20

1.30

2.00

2.50

2.10

2.40

3.10

2.20

11.5

00.

802.

601.

701.

80Eu

0.27

0.55

0.31

0.39

0.28

0.68

0.62

0.70

0.55

0.77

0.48

1.94

0.14

0.43

0.31

0.40

Gd

2.04

1.67

1.67

2.59

1.24

1.84

2.72

1.99

2.82

4.17

1.63

8.77

0.89

4.22

1.87

3.09

Tb0.

360.

280.

420.

650.

280.

300.

470.

320.

450.

720.

361.

220.

200.

640.

310.

65D

y3.

032.

172.

594.

381.

811.

793.

391.

903.

874.

632.

767.

161.

484.

312.

704.

39H

o0.

590.

450.

700.

760.

440.

450.

730.

430.

810.

900.

531.

020.

400.

930.

610.

95Er

2.06

1.61

2.34

3.14

1.44

1.27

2.19

1.35

3.16

3.05

2.05

3.33

1.28

2.59

2.00

2.86

Tm0.

360.

220.

440.

450.

270.

230.

320.

240.

510.

440.

320.

460.

230.

410.

280.

49Yb

2.04

1.97

2.75

3.68

1.75

1.37

2.16

1.56

3.53

3.38

2.49

3.49

1.78

2.54

2.16

3.39

Lu0.

310.

220.

400.

510.

220.

210.

300.

240.

490.

460.

420.

580.

320.

410.

310.

54

Nb/

Y0.

090.

070.

090.

100.

090.

110.

090.

080.

100.

060.

110.

080.

350.

090.

080.

05Zr

/Y4.

534.

085.

695.

074.

534.

044.

633.

645.

543.

755.

764.

2914

.54

3.00

5.01

3.30

Zr/N

b50

.47

59.7

860

.67

52.5

851

.91

36.6

953

.25

44.1

054

.52

62.7

151

.85

55.7

441

.74

33.7

363

.15

60.5

0AI

95.9

591

.19

87.8

792

.94

91.8

658

.06

96.1

355

.00

97.2

933

.62

84.6

792

.11

0.91

93.1

994

.32

97.4

6CC

PI61

.91

89.1

728

.72

32.4

777

.45

85.8

463

.59

97.1

871

.45

46.8

856

.11

54.1

39.

8472

.94

58.3

918

.94

La/Y

b2.

991.

071.

602.

070.

974.

313.

335.

771.

841.

782.

219.

572.

420.

942.

220.

74

LOI i

s lo

ss o

n ig

nitio

n, F

eOto

tal =

0.89

98*F

e 2O

3tota

l(R

agla

nd 1

989)

.


151

Table 4. Major and trace element compositions of the hanging-wall mafic volcanics and the altered dolerite dike from the Kutlular (Sürmene,Trabzon) mine. Abbreviations: AI– Ishikawa alteration index, CCPI– Chlorite-carbonate-pyrite index.

hanging-wall mafic volcanics altered dolerite dyke

K-8 K-20 K-27 KUPA1-1 KUPA1-3 KUPA3-6 KP3-6 KP3-7 KP3-8 KP4-6 K24 K-17 K-18A

SiO2 56.17 54.00 61.20 58.74 51.32 72.80 71.88 65.90 70.79 71.40 50.34 54.31 55.75

Al2O3 18.46 16.05 20.39 14.07 14.46 13.50 14.11 16.83 13.31 12.91 15.95 15.17 15.14

Fe2O3total 7.61 9.74 5.02 8.52 13.71 2.72 2.76 4.52 4.09 2.52 10.11 11.78 9.01

MgO 3.14 3.33 0.07 3.93 6.03 0.69 0.72 0.19 1.05 0.03 7.11 3.80 3.29

CaO 0.21 4.56 0.03 3.48 4.31 0.64 0.64 0.76 0.45 3.57 8.37 5.25 4.20

Na2O 6.10 5.35 0.02 4.41 2.71 4.85 4.89 5.62 6.07 3.41 2.41 3.37 5.49

K2O 0.04 0.04 0.08 0.01 0.11 1.02 1.20 0.06 0.16 0.14 0.09 0.14 0.26

TiO2 1.56 1.37 0.44 1.09 1.51 0.36 0.39 0.45 0.37 0.38 0.61 1.34 1.39

P2O5 0.23 0.27 0.06 0.26 0.20 0.06 0.06 0.04 0.03 0.06 0.07 0.29 0.27

MnO 0.19 0.14 0.05 0.10 0.15 0.09 0.09 0.08 0.08 0.05 0.18 0.22 0.36

LOI 6.20 5.10 12.50 5.40 5.50 3.20 3.10 5.40 3.40 5.30 3.50 4.30 4.80

Sum 99.91 99.95 99.86 100.01 100.01 99.93 99.84 99.85 99.80 99.77 98.74 99.97 99.96

FeOtotal 6.85 8.76 4.52 7.67 12.34 2.45 2.48 4.07 3.68 2.27 9.10 10.60 8.11

Cu 498.00 13.40 110.50 16.90 24.30 71.50 49.70 85.60 145.00 16.20 88.00 17.30 26.60

Pb 76.50 1.80 790.10 1.50 3.40 3.40 3.90 8.20 3.00 6.10 2.80 1.60 1.20

Zn 610.00 110.00 936.00 68.00 121.00 255.00 352.00 166.00 479.00 330.00 59.00 89.00 100.00

As 36.50 10.40 5.30 1.50 6.00 4.30 5.30 7.10 5.90 10.60 6.90 4.00 4.90

Ba 78.60 126.00 193.00 115.40 75.50 287.70 286.10 101.90 109.00 935.60 183.70 156.80 200.40

Y 17.10 31.10 27.30 28.70 21.40 26.90 24.50 26.70 25.20 20.90 15.00 28.50 27.20

Zr 57.50 66.30 136.00 76.40 46.70 129.90 123.10 138.20 107.00 118.10 21.70 59.40 59.50

Nb 1.50 1.70 2.60 1.90 1.30 2.30 2.30 2.50 1.80 2.00 0.50 1.70 1.80

Rb 0.60 0.80 1.60 <.5 0.60 16.20 16.70 0.70 4.40 <.5 0.80 2.00 4.30

Sr 63.80 313.90 22.00 142.70 137.90 207.40 202.10 37.60 59.90 57.20 274.90 268.70 296.30

Th 0.60 0.60 1.90 0.20 0.40 1.70 1.30 20.00 1.50 1.60 0.40 0.50 0.60

U 1.40 0.60 0.80 0.50 0.30 0.50 0.50 0.80 0.40 0.60 0.10 0.20 0.30

La 3.40 6.10 18.00 5.00 3.60 4.30 4.20 8.80 5.70 7.20 1.90 4.70 4.20

Ce 11.20 14.90 41.30 14.90 9.60 11.30 10.10 24.10 9.50 14.80 4.90 13.50 12.90

Pr 1.69 2.22 6.59 2.15 1.42 1.48 1.38 2.78 1.93 1.93 0.83 2.22 1.99

Nd 10.20 11.60 26.30 10.30 7.40 6.50 6.80 11.00 10.10 8.40 4.90 11.40 9.80

Sm 3.20 3.60 6.10 3.30 2.30 2.10 2.10 3.00 2.50 2.20 1.30 3.10 3.40

Eu 1.32 1.57 1.41 1.09 0.97 0.47 0.55 0.73 0.55 0.60 0.68 1.60 1.35

Gd 4.07 4.75 5.17 4.25 3.07 2.78 3.09 2.87 3.33 2.87 2.23 4.91 4.44

Tb 0.73 0.83 0.90 0.84 0.61 0.64 0.65 0.54 0.53 0.48 0.37 0.80 0.78

Dy 3.52 5.03 5.33 4.74 3.21 3.85 3.95 4.33 3.87 3.20 2.78 4.87 4.64

Ho 0.71 1.11 0.98 0.98 0.80 0.90 0.70 0.95 0.78 0.65 0.58 1.03 0.95

Er 1.80 3.12 2.99 2.78 2.16 2.78 2.84 3.28 2.73 2.45 1.50 2.97 2.79

Tm 0.27 0.65 0.46 0.50 0.35 0.51 0.53 0.57 0.42 0.37 0.23 0.48 0.45

Yb 1.44 2.84 3.60 2.63 1.92 2.90 3.62 3.90 2.88 2.91 1.44 2.88 2.38

Lu 0.31 0.47 0.54 0.42 0.33 0.50 0.49 0.57 0.45 0.40 0.27 0.42 0.39

Nb/Y 0.09 0.05 0.10 0.07 0.06 0.09 0.09 0.09 0.07 0.10 0.03 0.06 0.07

Zr/Y 3.36 2.13 4.98 2.66 2.18 4.83 5.02 5.18 4.25 5.65 1.45 2.08 2.19

Zr/Nb 38.33 39.00 52.31 40.21 35.92 56.48 53.52 55.28 59.44 59.05 43.40 34.94 33.06

AI 33.51 25.38 75.00 33.25 46.66 23.75 25.77 3.77 15.65 2.38 40.04 31.37 26.81

CCPI 61.93 69.17 97.87 72.45 86.69 34.83 34.47 42.84 43.16 39.29 86.64 80.40 66.47

La/Yb 2.36 2.15 5.00 1.90 1.88 1.48 1.16 2.26 1.98 2.47 1.32 1.63 1.76

LOI is loss on ignition, FeOtotal =0.8998*Fe2O3total (Ragland 1989).


152

0 100 200 300

Zr (ppm)

0

20

40

60

80

Y(p

pm

)

Calc-alkaline

Transitional

Tholeiitic

Zr/Y=7

Zr/Y=4.5

Zr/Y=2

b

0 2 4 6 8 10 12 14 16 18 20

La (ppm)

0

2

4

6

8Y

b(p

pm

)

La/Yb=1 La/Yb=3

La/Yb=6

a

Tholeiitic

Transitional

Calc-alkaline

altered dolerite dykehanging-wall mafic volcanicsfootwall rockslower dacites

Figure 6. Geochemical affinities of the Kutlular area volcanics (a) La versus Yb plot and (b) Zr versus Y plot.Discrimination lines from Barret & MacLean (1994, 1999).

Sr K2O Rb Ba Th Nb Ta CeP2O5 Zr TiO2 Y

0.01

0.1

1

10

100

1000

Sam

ple

/N-M

OR

B

hanging-wall mafic volcanics

K2O

b

P2O5 TiO2


0.01

0.1

1

10

100

1000

Sam

ple

/N-M

OR

B

altered dolerite dyke

K2O

d

P2O5 TiO2


0.01

0.1

1

10

100

1000

Sam

ple

/N-M

OR

B

lower dacites

K2O

a

P2O5 TiO2


0.01

0.1

1

10

100

1000

Sam

ple

/N-M

OR

B

footwall rocks

K2O

c

P2O5 TiO2

island arc calc-alkaline (Pearce 1983)

Figure 7. Spider diagrams of the Kutlular volcanics normalized to N-type MORB (normalizing values from Sun &McDonough 1989).

to 75. In the all types of rock from the study area, AIvalues increase towards the ore horizon that is consistentwith mineralogical observations. High AI values may bedue to the breakdown of plagioclase, volcanic glass andtheir replacement by illite (Tables 3 & 4).

The Ishikawa index has two limitations: (i) it does notenable separation of chlorite-from sericite-rich alterationand (ii) it does not consider carbonate alteration. Forthese reasons, the chlorite-carbonate-pyrite index (CCPI=100*(MgO+FeOtotal)/(MgO+FeOtotal+Na2O+K2O) were usedto distinguish samples with high chlorite content. CCPIvalues of hanging wall mafic volcanics and altered doleritedyke fluctuate between 34.47 and 97.87 and footwallvolcanics range from 9.84 to 99.92 (Tables 3 & 4).Hanging wall mafic rocks and footwall felsic rocksgenerally have high CCPI values, indicating the importanceof chlorite and pyrite formation in these rocks.

Mass Balance Calculations

During alteration, some elements are mobile whereasothers are relatively immobile and become enriched in theresidual rock. The extent of element mobility duringalteration of the footwall and hanging-wall rocks ofmassive ore can be estimated using the method ofMacLean & Kranidiotis (1987). Mass changes inhydrothermal alteration zones associated with VMSdeposits yield quantitative information on hydrothermalalteration and fluid-rock interaction. Immobile elementgeochemical methods allow the determination of primaryfractionation trends in volcanic rocks, subsequent masschanges, and the recognition of volcanic units in alteredsequences. Although the method does not considerneither possible change in the density of the primary rocknor changes in the primary rock volume (MacLean 1990),


153

aLa Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

0.1

1

10

100

1000S

am

ple

/Chon

dri

telower dacites

b

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

0.1

1

10

100

1000

Sa

mp

le/C

ho

ndri

te

hanging-wall mafic volcanics

d


0.1

1

10

100

1000

Sam

ple

/Ch

on

dri

te

altered dolerite dyke

c


0.01

0.1

1

10

100

1000

Sa

mp

le/C

hon

dri

te

footwall rocks

Figure 8. REE patterns of the Kutlular volcanics normalized to chondrite values (Taylor & McLennan 1985) showingenrichment and depletion of REE during the alteration processes.

the mass-balance calculations can be used to identify therelative gains or losses of elements during ore formation.

All the rock samples (Tables 3 & 4) analyzed wereseparated into 4 main types of alteration groups, basedon petrographic studies, chemical and XRD analyses.These are illite zone, chlorite zone, interstratifiedillite/smectite zone and smectite zone. In the footwalldacite, illite zone, interstratified illite/smectite zone withsilicification, and smectite zone were observed fromcentral part to outer zone of ore whereas in the hanging-wall rocks chlorite alteration is common. These alterationgroups were also examined by means of mass balancecalculations using the MINSQ computer program(Hermann & Berry 2002; Table 5). Mass changecalculations were applied to groups of different alterationmineralogy in footwall and lower dacites using singleprecursor method of MacLean and Kranidiotis (1987). Inthe calculations, Zr owing to its immobile character andhigh correlation coefficients with the other elements, andthe least altered dacite composition of Akçay (2008) dueto the lack of fresh footwall dacite composition in thestudied area were used. The least altered dacitecomposition of Akçay (2008) is the mean of ten dacites,collected from footwall rocks of eastern Pontide massivesulfide deposits and is stratigraphically equivalent to thoseof Kutlular area (Table 6, Figure 9). For the mass-balancecalculations, the means of anhydrous equivalent of thesegroups are recalculated. The equation used in thecalculations can be written for SiO2 as follows (MacLean &Kranidiotis 1987):

Using the above equation, calculations were done for eachelement (RC) and in order to determine mass gains andlosses (ΔCi), least altered dacite composition aresubtracted from the values of RC.

Hydrothermal alteration around the Kutlular VMSdeposit caused mass increases within the illite/smectitezone and the illite zone with silicification, whereasdecreases can be noted within smectite zone of thefootwall dacite and lower dacites (Table 6). Overall, REEwere depleted within footwall and lower dacites. The illitezone is characterized by SiO2 and Fe2O3

total increases of99.68 and 6.40 g/100 g rock, respectively. CaO and Na2Owere depleted while K2O was enriched, owing tosericitization of plagioclase. In this zone, the total mass

gain is 105.36 g/100 g rock, which is met by addition ofquartz and pyrite. Mobile trace elements increasedsignificantly, with the highest change in Cu (762.56g/100 g rock). Ba considerably was depleted, probablydue to the complete destruction of feldspar. Theillite/smectite interstratified clay mineral zone exhibitsimilar characteristics but different degree of enrichmentsor depletions. Mass gain in this group is 54.97 g/100 g.Except for SiO2 and Fe2O3

total, all other major elementswere slightly depleted. Changes in relative abundances ofCaO and Na2O may be interpreted as alkali elementleaching in spite of the fact that these elements weretaken up during smectite formation. Smectitic alterationresulted in a significant decrease in SiO2. In the lowerdacites, SiO2 is depleted while Al2O3 and Fe2O3

total wereenriched due to the argillization and hematitization.During the hydrothermal alteration Zr and Nb behaveimmobile but Y is generally mobile in character.


154

Table 5. Calculated mineralogical compositions using the MINSQmethod of Hermann & Berry (2002) from major elementchemistry (Tables 3 & 4) of groups of footwall and hangingwall mafic volcanics with similar hydrothermal alterationpattern.

footwall volcanics hanging-wall

mafic volcanics

smectite illite/smectite illite zone + Fe-rich Mg-rich

zone zone silicification chlorite chlorite

Mean (5) Mean (5) Mean (6) Mean (8) Mean (4)

quartz 22.95 55.97 68.26 20.16 23.62

smectite 34.05 0.02 0.00 4.44 5.15

kaolinite 19.29 0.58 0.00 8.69 13.30

illite 0.00 0.52 18.72 3.50 0.85

illite/smectite 0.00 9.88 1.81 2.27 2.15

Fe-chlorite 0.00 0.57 0.00 7.83 4.53

Mg-chlorite 0.00 0.00 0.00 1.34 6.49

tosudite 0.00 0.00 0.00 0.36 0.17

palygorskite 0.00 0.23 0.00 0.00 0.00

albite 4.00 5.48 0.00 26.27 28.46

anorthite 0.01 0.01 0.00 4.55 0.00

K-feldspar 10.41 1.90 2.90 0.62 0.00

augite 0.00 0.00 0.00 12.40 6.07

pyrite 0.60 12.46 5.41 0.06 0.03

hematite 2.21 3.30 0.05 0.00 2.12

ilmenite 0.00 0.00 0.00 1.68 1.44

epidote 0.00 0.00 0.00 1.60 1.95

accessory 0.34 1.95 0.30 0.32 0.04

sum 93.87 92.86 97.46 96.08 96.34

res SSQ 0.22 0.62 0.12 0.09 0.14

( )( %)

( . ) ( – )SiO Zr ppmSiO Wt

alt rock Zr ppm freshrock22

#=


155

Tabl

e 6.

Aver

age

chem

ical

com

posi

tions

of

grou

ps o

f fo

otw

all

rock

s w

ith s

imila

r hy

drot

herm

al a

ltera

tion

patt

ern,

and

the

ir r

econ

stru

cted

com

posi

tions

(R

C) a

nd n

et m

ass

chan

ges

(ΔC i

)ca

lcul

ated

usi

ng t

he m

etho

d of

Mac

Lean

&K

rani

diot

is (

1987

). C

ompo

sitio

nal v

alue

s fo

r th

e ox

ides

are

in %

and

all

othe

r el

emen

ts in

ppm

, an

d m

ass

chan

ges

for

them

are

in g

/100

gro

ck a

nd in

ppm

/100

g r

ock,

res

pect

ivel

y. T

he le

ast

alte

red

daci

te c

ompo

sitio

n is

fro

m A

kçay

(20

08).

low

er d

acite

sfo

otw

all v

olca

nics

leas

tlo

wer

RC

ΔC i

smec

tite

RC

ΔC i

I/SR

CΔ

C iill

iteR

CΔ

C ial

tere

dda

cite

szo

nezo

nezo

ne

SiO

275

.77

73.3

972

.12

-3.6

570

.99

66.6

6-9

.11

76.8

811

9.14

43.3

785

.43

175.

4599

.68

Al2O

312

.47

17.7

417

.43

4.96

20.9

119

.64

7.17

6.74

10.4

5-2

.02

7.83

16.0

73.

60Fe

2O3to

tal

2.61

5.08

4.99

2.38

3.61

3.39

0.78

13.4

720

.87

18.2

64.

399.

016.

40M

gO0.

890.

660.

65-0

.24

0.86

0.81

-0.0

80.

190.

29-0

.60

0.28

0.57

-0.3

2Ca

O1.

950.

090.

09-1

.86

0.11

0.10

-1.8

50.

500.

77-1

.18

0.13

0.26

-1.6

9N

a 2O

3.59

1.90

1.87

-1.7

20.

960.

91-2

.68

0.84

1.30

-2.2

90.

030.

07-3

.52

K2O

2.24

0.57

0.56

-1.6

82.

091.

96-0

.28

0.61

0.94

-1.3

01.

753.

591.

35Ti

O2

0.33

0.46

0.45

0.12

0.39

0.36

0.03

0.65

1.01

0.68

0.14

0.28

-0.0

5P 2

O5

0.07

0.03

0.02

-0.0

50.

040.

04-0

.03

0.06

0.10

0.03

0.01

0.03

-0.0

4M

nO0.

070.

090.

090.

020.

030.

03-0

.04

0.06

0.10

0.03

0.01

0.02

-0.0

5Cr

2O3

0.00

0.00

0.00

0.00

0.01

0.01

0.01

0.00

0.00

0.00

0.00

0.00

0.00

Sum

100.

0010

0.00

98.2

7-1

.73

100.

0093

.91

-6.0

910

0.00

154.

9754

.97

100.

0020

5.36

105.

36

Cu6.

9018

8.48

185.

2217

8.32

127.

9412

0.15

113.

2511

2.18

173.

8416

6.94

374.

6876

9.46

762.

56Pb

10.7

03.

113.

06-7

.64

206.

0019

3.45

182.

7515

9.84

247.

7023

7.00

45.6

893

.82

83.1

2Zn

68.9

023

4.22

230.

1716

1.27

23.6

022

.16

-46.

7422

04.2

034

15.7

833

46.8

812

8.17

263.

2119

4.31

As5.

403.

193.

13-2

.27

131.

2812

3.28

117.

8812

5.62

194.

6718

9.27

91.6

518

8.22

182.

82Ba

468.

7015

3.93

151.

27-3

17.4

372

3.62

679.

5521

0.85

886.

9613

74.4

990

5.79

141.

6329

0.86

-177

.84

Y34

.40

54.9

854

.03

19.6

326

.70

25.0

7-9

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16.0

624

.89

-9.5

116

.08

33.0

3-1

.37

Zr15

8.50

161.

2915

8.50

0.00

168.

7815

8.50

0.00

102.

2815

8.50

0.00

77.1

815

8.51

0.01

Nb

5.80

2.99

2.94

-2.8

63.

082.

89-2

.91

2.20

3.41

-2.3

91.

372.

81-2

.99

La17

.10

10.8

210

.64

-6.4

62.

001.

88-1

5.22

7.66

11.8

7-5

.23

4.38

9.00

-8.1

0Ce

29.3

018

.13

17.8

2-1

1.48

4.82

4.53

-24.

7716

.60

25.7

2-3

.58

8.98

18.4

5-1

0.85

Pr4.

204.

344.

260.

060.

460.

44-3

.76

1.96

3.04

-1.1

61.

252.

57-1

.63

Nd

18.8

019

.54

19.2

10.

412.

422.

27-1

6.53

7.14

11.0

6-7

.74

4.92

10.1

0-8

.70

Sm4.

305.

665.

561.

261.

141.

07-3

.23

2.02

3.13

-1.1

71.

703.

49-0

.81

Eu1.

001.

441.

420.

420.

300.

29-0

.71

0.52

0.80

-0.2

00.

390.

80-0

.20

Gd

5.00

7.44

7.31

2.31

2.36

2.22

-2.7

82.

203.

42-1

.58

1.87

3.84

-1.1

6Tb

6.20

1.29

1.27

-4.9

30.

570.

54-5

.66

0.42

0.65

-5.5

50.

350.

73-5

.47

Dy

6.20

8.60

8.45

2.25

3.97

3.73

-2.4

72.

854.

42-1

.78

2.62

5.37

-0.8

3Er

4.20

5.44

5.35

1.15

2.89

2.71

-1.4

92.

073.

21-0

.99

1.94

3.98

-0.2

2Yb

4.20

5.96

5.86

1.66

3.55

3.34

-0.8

62.

313.

58-0

.62

2.14

4.39

0.19

Lu0.

700.

920.

900.

200.

570.

53-0

.17

0.37

0.57

-0.1

30.

290.

60-0

.10

Tota

l REE

-13.

16-7

7.66

-29.

72-3

7.88

Discussion

The argillic zones of the massive sulfide alteration haloecontain mixed layer illite/smectite, illite, Fe-Mg chloriteand kaolin group minerals and are characterized bytransformations in the mixed layer and the kaolinitepolytypes with proximity to the orebodies (Inoue & Utada

1983; Inoue et al. 1988; Marumo 1989). In the footwallfelsic rocks of the Kutlular area, occurrences ofinterstratified illite/smectite (I/S), which are characteristicminerals of neutral to alkaline types of alteration in felsicrocks (Inoue 1995), may be considered intermediateproducts in the smectite to illite sequence of mineral


156

-6

-4

-2

0

2

4

6

8

ne

tm

ass

cha

ng

e

-12

-10

-8

-6

-4

-2

0

2

4

6

8

10

ne

tm

ass

ch

ang

e

-20

0

20

40

60

80

100

ne

tm

ass

ch

ang

e

-20

0

20

40

60

80

100

ne

tm

ass

cha

ng

e

lower dacites

smectite zone

illite/smectite zone

illite zone + silicification

-400

-300

-200

-100

0

100

200

ne

tm

ass

cha

ng

e

-100

0

100

200

300ne

tm

ass

cha

ng

e

-200

0

200

400

600

800

ne

tm

ass

ch

ang

e-1000

0

1000

2000

3000

4000

ne

tm

ass

ch

an

ge

lower dacites

smectite zone

illite/smectite zone

illite zone + silicification

SiO

2

TiO

2

Al 2O

3

Fe

2O

3to

tal

MnO

MgO

Ca

O

Na

2O

K2O

P2O

5

Cu

Pb

Zn

As

Ba Y Zr

Nb

�R

EE

Figure 9. Bar plots showing average net mass changes for grouped rocks regarding clay mineralogy anddegree of alteration. In calculations, the method of MacLean & Kranidiotis (1987) and theleast altered dacite composition of Akçay (2008) were used. Values are g/100 g for the majoroxides, and in ppm/100 g for trace elements.

transformation as a result of increasing temperaturetowards the ore horizon. Since illite’s stabilitytemperature ranges from about 200° to 300 °C, it can beused as a geothermometer of prograde thermal effects.At temperatures less than about 200 °C, interlayeredillite/smectite or discrete smectite prevails and mayoverprint pre-existing illite. Besides, illite forms in thepresence of weakly acidic (CO2-rich) fluids (Steiner 1968;Horton 1985; Simmons & Browne 1990).

In the alteration haloes of the Kutlular area, kaolingroup minerals accompany the smectite within themarginal argillic zone, and these are not observed withinthe inner alteration horizon. It is known that kaolin groupminerals form under low-temperature conditions (<150–200 °C) and are indicative of formation at a pH of around3-4 (Hemley et al. 1980; Sillitoe 1993; Arribas 1995).The alteration mineral paragenesis of the Kutlular areasuggest that the hydrothermal solutions were acidicduring the formation of the ore body, kaolinite-halloysiteand illite zones, but became alkaline with decreasingtemperature towards to the end of ore deposition.

In the Kutlular area, the chlorite alteration occupiestypically the innermost alteration zone, and passesoutward into the illite alteration. The basaltic and basalticandesites around the ore body contain chloriteaccompanying epidote and albite, indicating an alterationtemperature around 200 °C (i.e. Inoue 1995). Chloritewas observed as replacements of mafic phenocrysts, glassand void infillings. It is possible to see chlorite also asinclusion in albitized plagioclase. In the studied deposit,the composition of chlorite may vary from Fe-richadjacent to massive sulphide mineralization, to Mg-rich onthe periphery of mineralized zones. This occursparticularly in Precambrian deposits, whereas youngerdeposits may be dominated by Mg-rich chlorite. Mg-richchlorite is considered to result from the interaction ofcold seawater with hot hydrothermal fluids (Allen 1988;Franklin et al. 1981; Santaguida et al. 1992). In case ofthe high Fe/Mg ratio, glass, plagioclase and sericite areconverted to chlorite (Barrett & MacLean 1994). Thisprocess can be formulated by the chemical reaction givenby Large et al. (2001) as follows:

Using these reaction, it can be easily explained why illitewere rarely seen in the chlorite zone of the studied area(e.g., Sangster 1972; Lydon 1988; Large 1992; Lentz1999; Schardt et al. 2001). With decreasingtemperature, chlorite gradually changes tochlorite/smectite, illite/smectite and smectite towards tothe outer zone away from the ore body.

The zeolites which are commonly present in thehydrothermal systems can be classified as Na, Ca- and Ca-Mg series of alteration (Inoue 1995). In the studied area,mordenite, heulandite, stilbite, laumontite and analcimeare determined which characterize the Ca- and Na-type ofalteration. With decreasing temperature, Ca-zeolites(laumontite, heulandite, stilbite) and Na-zeolite (analcime)are determined from centre to margin of the ore horizonas void infillings and replacement of plagioclase. Na-typealteration is reported by Utada & Ishikawa (1973) at themarginal zones in some Kuroko-type alteration withextensive occurrences of analcime and Na-smectite.

Textural (e.g., Khin & Large 1992; Sharpe & Gemmell2001) and chemical evidence (e.g., Herrmann & Hill2001; Large et al. 2001) imply that direct precipitation isnot as important as void infilligs and selectivereplacements of the volcanic components on the sea floor.In these cases, formation of carbonate minerals involvesmixing of hydrothermal fluids and seawater below the seafloor in permeable volcanic units (e.g., Hermann & Hill2001). It is also reported that the carbonate formationresults from a mixing of small amounts of magmatic CO2-rich fluid with seawater at or below the palaeo-sea floor(Khin Zaw & Large 1992; Callaghan 2001). In the studyarea, calcite is determined in the chlorite zone close to theore within the fracture and pores of the basalt andbasaltic andesite, and has low intensity. The source of Camight be plagioclase and Ca-rich clinopyroxene. Theformation of calcite can be explained by the followingreaction:


157

( )

( )

KAl Si O OH H SiO

sericite Fe Mg H O

Mg Fe Al Si O OH K Hchlorite

2 3

9 6 18

3 2 28

3 3 10 2 4 4

2 22

2 3 2 3 10 8

+ +

+ +

+ +

+ +

+ +

CaO CO H OH CaCO H Ocalcite

2 3 2+ + + ++ -

( )

6 3

NaAl Si O K H KAl Si O OHalbite sericite

SiO Naquartz

3 23 3 8 3 3 10 2

2

+ + +

+

+ +

+

Calculated mass changes in the footwall dacitescommonly are large, and result from major silica masstransfer. Mass-change calculations indicate that CaO +Na2O + MgO were leached from the rocks byhydrothermal solutions, whereas large amounts ofhydrothermal Fe2O3total were added. Hanging wall basaltand basaltic andesite show mass changes that aregenerally much smaller than in the footwall.

Conclusions

Alteration geology, mineralogy and geochemistry studiesof the Kutlular (Sürmene, Trabzon) area reveals followingfindings:

(1) The mineralogic and petrographic investigations ofthe Kutlular massive sulphide deposit footwall andhanging-wall rocks reveal that smectite,illite/smectite, illite and chlorite are abundant clayminerals to proximity of the ore. The other clayminerals are kaolinite and chlorite/smectite. Allthese hydrothermal mineral assemblages areaccompanied by silica polymorphous.

(2) The clay mineralogy studies indicate thatsilicification+pyrite+illite zone, illite+silicificationzone, illite/smectite+silification zone and smectitezone accompanying kaolinite and halloysite arepresent in the footwall rocks whereas chloritezone is well developed in the mafic volcanics.

(3) Immobile trace and rare-earth element dataindicate that the footwall and hanging-wall

volcanic rocks transitional between tholeiitic andcalc-alkaline in character. The trace elementspatterns of the samples show considerable LILEenrichment (K, Rb, Ba) and depletion in Sr, La andTi relative to N-MORB.

(4) Chondrite-normalized REE patterns of thevolcanics show a pronounced HREE enrichment.Additionally, the volcanic rocks have differentdegree of positive and negative Eu and Ceanomalies implying different degree ofhydrothermal alteration resulted of interactionwith sulphide-sulphate ore forming fluids.

(5) The Kutlular area footwall and hanging-wallalteration zones have several geochemicalcharacteristics that show systematic changes withincreasing proximity to the ore. These include Nadepletion and elevated alteration index (AI),chlorite-carbonate-pyrite index (CCPI).

Acknowledgements

This paper is a part of PhD study of the first author, andsupported by Karadeniz Technical University ScientificResearch Fund (Project 2005.112.005.3). The authorsthank to Nilgün Güleç (Middle East Technical University,Ankara) and Durmuş Boztuğ (Cumhuriyet University,Sivas) for their editorial comments and suggestions. Thecritical reviews from Ömer Işık Ece (İstanbul TechnicalUniversity, İstanbul) and an anonymous reviewer aregreatly appreciated.


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